Twisted leak detection cable

ABSTRACT

Disclosed is a leak detection cable that has an outer jacket layer and a four wire construction in a flat wire configuration that is twisted in a helix. Detection cables are disposed on the exterior surface adjacent openings of the jacket to allow for detection of aqueous fluids. The wire is twisted in a helix to allow adjacent detector wires to easily detect aqueous fluids. Disparate materials are used for the jacket and the coatings of the wires, to allow the jacket to be easily removed from the wires without affecting the integrity of the coatings of the wires. The four flat wire configuration is sized and spaced for easy connection to an insulation displacement connector.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a Non-Provisional Patent Application of U.S.Provisional Patent Application No. 61/059,634, entitled “TWISTED LEAKDETECTION CABLE”, and filed Jun. 6, 2008, by Donald M. Raymond. Theentire content of the above-mentioned application and the U.S.Provisional Patent Application filed May 12, 2009, by Donald M. Raymond,entitled “Aqueous Chemical Leak Detection Cable” are hereby specificallyincorporated herein by reference for all they disclose and teach.

BACKGROUND OF THE INVENTION

Leak detection cables have been used to detect moisture in variousapplications. For example, leak detection cables may be used to detectleakage from appliances that leak water, such as dishwashers, hot waterheaters, etc., in normal household applications, as well as incommercial applications. Leak detection systems may be used toautomatically cut off water supplies, such as electrical and gassupplies, as well as providing notification for maintenance and repairservices. These systems have been valuable in preventing flood damageand other damage.

SUMMARY OF THE INVENTION

An embodiment of the present invention may therefore comprise a leakdetection cable comprising: a first detector conductor comprising: afirst detector wire; a first conductive covering surrounding the firstdetector wire that comprises a preselected conductive plastic; a firstfeedback conductor disposed adjacent to the first detector wire thatdefines a plane with the first detector conductor comprising: a firstfeedback wire; a first insulating covering surrounding a preselectednon-conductive plastic; a second feedback conductor disposed in theplane adjacent to the first feedback connector comprising: a secondfeedback wire; a second insulating covering surrounding the secondfeedback wire that comprises the preselected non-conductive plastic; asecond detector conductor disposed in the plane adjacent to the secondfeedback connector comprising: a second detector wire; a secondconductive covering surrounding the second detector wire that comprisesthe preselected conductive plastic; a jacket that surrounds the firstfeedback conductor and the second feedback conductor and partiallysurrounds the first detector conductor and the second detector conductorby an amount that is sufficient to hold the first detector conductor andthe second detector conductor and provides openings adjacent to thefirst conductive covering and the second conductive covering to allowexposure to aqueous fluids, the jacket made from a plastic jacketmaterial that is dissimilar to, and has low adhesion with, thepreselected conductive plastic and the preselected non-conductiveplastic so that the jacket can be easily removed from the first detectorconductor, the second detector conductor, the first feedback conductorand the second feedback conductor.

An embodiment of the present invention may further comprise a methodmaking a leak detection cable comprising: extruding a first conductivecovering, that comprises a preselected conductive plastic, around afirst detector wire to form a first detector conductor; extruding asecond conductive covering, that comprises the preselected conductiveplastic, around a second detector wire to form a second detectorconductor; extruding a first non-conductive covering, that comprises apreselected non-conductive plastic, around a first feedback wire to forma first feedback conductor; extruding a second non-conductive covering,that comprises the preselected non-conductive plastic, around a secondfeedback wire to form a second feedback conductor; placing the firstfeedback conductor adjacent to the first detector conductor to form aplane; placing the second feedback conductor adjacent to the firstfeedback conductor in the plane; placing the second detector conductoradjacent to the second feedback conductor in the plane; extruding ajacket around the first detector conductor, the first feedbackconductor, the second feedback conductor and the second detectorconductor so that the first feedback conductor and the second feedbackconductor are substantially surrounded by the jacket, and the firstdetector conductor and the second detector conductor are partiallysurrounded by the jacket by an amount sufficient to hold the firstdetector conductor and the second detector conductor in the jacket andprovide openings adjacent to the first detector conductor and the seconddetector conductor to allow exposure to aqueous fluids, the jacketcomprising a plastic jacket material that is dissimilar to, and has lowadhesion with, the preselected conductive plastic and the preselectednon-conductive plastic so that the jacket can be easily removed from thefirst detector conductor, the first feedback conductor, the secondfeedback conductor and the second detector conductor.

An embodiment of the present invention may therefore further comprise aleak detection cable comprising: at least one detector conductorcomprising: a detector wire; a conductive covering surrounding thedetector wire that comprises a preselected conductive plastic; at leastone feedback conductor disposed adjacent to the detector wire thatdefines a plane with the detector conductor comprising: a feedback wire;an insulative covering surrounding a preselected non-conductive plastic;a jacket that surrounds the at least one feedback conductor andpartially surrounds the at least one detector conductor by an amountthat is sufficient to hold the first detector conductor and providesopenings adjacent to the conductive coating to allow exposure to aqueousfluids, the jacket made from a plastic jacket material that isdissimilar to, and has low adhesion with, the preselected conductiveplastic and the preselected non-conductive plastic so that the jacketcan be easily removed from the at least one detector conductor and theat least one feedback conductor.

An embodiment of the present invention may therefore further comprise amethod making a leak detection cable comprising: extruding a conductivecoating, that comprises a preselected conductive plastic, around atleast one detector wire to form a detector conductor; extruding anon-conductive coating, that comprises a preselected non-conductiveplastic, around at least one feedback wire to form a feedback conductor;placing the feedback conductor adjacent to the detector conductor toform a plane; extruding a jacket around the detector conductor and thefeedback conductor so that the feedback conductor is substantiallysurrounded by the jacket, and the detector conductor is partiallysurrounded by the jacket by an amount sufficient to hold the detectorconductor in the jacket and provide an opening adjacent to the detectorconductor to allow exposure to aqueous fluids, the jacket comprising aplastic jacket material that is dissimilar to, and has low adhesionwith, the preselected conductive plastic and the preselectednon-conductive plastic so that the jacket can be easily removed from thedetector conductor and the feedback conductor.

An embodiment of the present invention may therefore further comprise aleak detection cable comprising: at least one detector conductorcomprising: a detector wire; a covering surrounding the detector wire; ajacket that partially surrounds the at least one detector conductor byan amount that is sufficient to hold the detector conductor and providesan opening adjacent to the covering to allow exposure to aqueous fluids,the jacket made from a plastic jacket material that is dissimilar to,and has low adhesion with, the preselected conductive plastic so thatthe jacket can be easily removed from the at least one detectorconductor.

An embodiment of the present invention may therefore further comprise amethod for making a leak detection cable comprising: extruding aconductive coating, that comprises a preselected conductive plastic,around at least one detector wire to form a detector conductor;extruding a jacket around the detector conductor, so that the detectorconductor is partially surrounded by the jacket by an amount sufficientto hold the detector conductor in the jacket and provide an openingadjacent to the detector conductor to allow exposure to aqueous fluids,the jacket comprising a plastic jacket material that is dissimilar to,and has low adhesion with, the preselected conductive plastic and thepreselected non-conductive plastic so that the jacket can be easilyremoved from the detector conductor.

An embodiment of the present invention may therefore further comprise aleak detection cable comprising: a first detector conductor comprising:a first detector wire; a first detector covering surrounding the firstdetector wire; a first feedback conductor disposed adjacent to the firstdetector wire that defines a plane with the first detector conductorcomprising: a first feedback wire; a first insulating coveringsurrounding a preselected non-conductive plastic; a second feedbackconductor disposed in the plane adjacent to the first feedback connectorcomprising: a second feedback wire; a second insulating coveringsurrounding the second feedback wire that comprises the preselectednon-conductive plastic; a second detector conductor disposed in theplane adjacent to the second feedback connector comprising: a seconddetector wire; a second detector covering surrounding the seconddetector wire; a jacket that surrounds the first feedback conductor andthe second feedback conductor and partially surrounds the first detectorconductor and the second detector conductor by an amount that issufficient to hold the first detector conductor and the second detectorconductor and provides opening adjacent to the first detector coveringand the second detector covering to allow exposure to aqueous fluids,the jacket made from a plastic jacket material that is dissimilar to,and has low adhesion with, the detector covering and the preselectednon-conductive plastic so that the jacket can be easily removed from thefirst detector conductor, the second detector conductor, the firstfeedback conductor and the second feedback conductor, the jacket twistedin a helical configuration so as to sequentially expose the firstdetector conductor and the second detector conductor.

An embodiment of the present invention may therefore further comprise amethod of making a leak detection cable comprising: placing a firstdetector covering around a first detector wire to form a first detectorconductor; placing a second detector covering around a second detectorwire to form a second detector conductor; placing a first non-conductivecovering, that comprises a preselected non-conductive plastic, around afirst feedback wire to form a first feedback conductor; placing a secondnon-conductive covering, that comprises the preselected non-conductiveplastic, around a second feedback wire to form a second feedbackconductor; placing the first feedback conductor adjacent to the firstdetector conductor to form a plane; placing the second feedbackconductor adjacent to the first feedback conductor in the plane; placingthe second detector conductor adjacent to the second feedback conductorin the plane; extruding a jacket around the first detector conductor,the first feedback conductor, the second feedback conductor and thesecond detector conductor so that the first feedback conductor and thesecond feedback conductor are substantially surrounded by the jacket,and the first detector conductor and the second detector conductor arepartially surrounded by the jacket by an amount sufficient to hold thefirst detector conductor and the second detector conductor in the jacketand provide openings adjacent to the first detector conductor and thesecond detector conductor to allow exposure to aqueous fluids, thejacket comprising a plastic jacket material that is dissimilar to, andhas low adhesion with, the first detector covering, the second detectorcovering and the preselected non-conductive plastic so that the jacketcan be easily removed from the first detector conductor, the firstfeedback conductor, the second feedback conductor and the seconddetector conductor; twisting the jacket in a helix so that the firstdetector conductor and the second detector conductor are sequentiallyexposed along a linear surface of leak detection cable.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric diagram of one embodiment of the invention.

FIG. 2 is a cross-sectional view of the embodiment of FIG. 1.

FIG. 3 is a cross-sectional view of another embodiment of the invention.

FIG. 4 is a cross-sectional view of another embodiment of the invention.

FIG. 5 is an isometric view of a leak detection cable with an insulationdisplacement connector.

FIG. 6 is a cutaway side view of an extrusion molding device.

FIG. 7 is a close-up view of a portion of FIG. 6.

FIG. 8 is an end view of the die.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1 is an isometric view of an embodiment of a leak detection cable100. As shown in FIG. 1, the leak detection cable includes a jacket 102that surrounds four conductors 104-110. Conductors 104, 106 are detectorconductors that have a waterproof, conductive covering. Alternatively,the detector conductors 104, 106 can be covered with a braided coverthat allows water to penetrate the braided cover and contact thedetector wire disposed within the detector conductors 104, 106. Whenwaterproof conductive coatings are used, the wire inside the conductors104, 106 is protected from corrosion, while allowing conduction throughthe coating to the wires in conductors 104,106. The conductive coatingalso increases the surface area of the detector wire which increases thesensitivity of the leak detection cable 100. Conductors 108, 110comprise feedback conductors that provide information regarding thelocation or presence of the detected leak, such as through conductivity,ratiometric measurement, time domain reflectometry or other methods.Although two feedback conductors 108, 110 are shown in FIGS. 1 and 2,leak detection systems can operate with a single feedback conductor, orno feedback conductors. Also, additional feedback conductors can beutilized. Although two feedback conductors are illustrated in FIGS. 1and 2, any number or no feedback conductors may be utilized in thevarious embodiments disclosed. As shown in FIG. 1, the conductors104-110 are embedded in the jacket 102. The detector wires 108, 110 thathave non-conductive insulators, are placed between the detectorconductors 104, 106 in the jacket 102. Detector conductors 104, 106 aretherefore disposed at the edges of the jacket 102 and are only partiallyembedded in the jacket 102 so that the outer edges of the detectorconductors 104, 106 are exposed. Although two detector conductors 104,106 are illustrated in FIGS. 1 and 2, moisture detector systems willoperate with a single detector conductor. Similarly, although theembodiments disclosed herein show two feedback conductors, the variousembodiments may operate with a single feedback conductor or no feedbackconductor.

As shown in FIG. 1, jacket 102 is then heated and twisted to form ahelix. The material of the jacket 102 is a cross-linked polymer, which,when heated above a certain level, can be twisted into a helix. When thecross-linked polymer cools, it crystallizes, so that the twist is heldin place. Openings 114, 112, that are adjacent to detector conductors104, 106, spiral around the outer surface of the leak detection cable100, so that when water is disposed between adjacent openings 114, 112,a conductive path is created between detector conductors 104, 106,respectively. Further, the conductors 104-110 are disposed in the jacket102 in a four flat configuration that has a spacing that matchesstandard four flat connectors, such as an insulation displacementconnector 502 (FIG. 5), including an RJ-11 connector. This allows theleak detection cable 100 to be easily connected in the field.

FIG. 2 is a cutaway view of the leak detection cable 100 illustrated inFIG. 1. As shown in FIG. 2, jacket 102 surrounds the four conductors104, 106, 108, 110. Jacket 102 has openings 112, 114 that are adjacentdetector conductors 106, 104, respectively. The openings 112, 114 injacket 102 expose the coverings 214, 202, of detector conductors 106,104 to the exterior environment outside of the jacket 102. The coverings202, 214 may comprise conductive coatings that allow conduction to thedetector wires 204, 216, or may comprise braided coverings that allowwater to penetrate the openings in the braided covering to allowconduction between the detector wires 204, 216. Since the cable istwisted, the opening 112 and the opening 114 may be resting in a pool ofwater from a leak, such as a leak from a hot water heater. Water has acertain amount of conductivity that provides a conductive path betweenopenings 112, 114 to detector conductors 106, 104, respectively.Conductive coating 214 transmits electrical signals to the detector wire216. Similarly, conductive coating 202 transmits electrical signals todetector wire 204. When there is a conductive path between openings 112,114, as a result of a pool of water, electrical signals are transmittedbetween the detector wires 204, 216 to indicate the location of theleak. Feedback conductor 108 comprises a feedback wire 208 and aninsulating coating 206. Feedback conductor 110 comprises a feedback wire212 having an insulating coating 210. The insulating coatings 206, 210separate the conductive coatings 202, 214 of the detector conductors104, 106 and also provide insulation around the feedback wires 208, 212.Feedback conductors 108, 110 assist in detecting the location orpresence of the leak, such as by use of conductivity, ratiometricmeasurement, time domain reflectometry or other methods. As shown inFIG. 2, the center point of detector wire 204, feedback wire 208,feedback wire 212 and detector wire 216 are evenly spaced along ahorizontal plane. The substantially equal spacing of these detectorsallows for the use of four flat connectors, such as the insulationdisplacement connector 502 (FIG. 5). The insulation displacementconnector 502 (FIG. 5) is connected to the four flat wire set that isexposed after the jacket 102 is stripped from the conductors 104, 106,108, 110. For example, the insulation displacement connector may be anRJ-11 type of connector.

The materials of the jacket 102 and the coatings 202, 206, 210, 214 maybe made from dissimilar plastics. The dissimilar plastics provide easein stripping away the jacket 102 from the coatings 202, 206, 210, 214.Again, the ability to strip away the jacket 102 from the four flat wirearray allows the insulation displacement connector 502 to be easilyclipped onto the end of the leak detector cable 100.

Prior to installation of the connector 502, the cable is twisted, asdisclosed above, in a continuous helix. For example, the helix may haveapproximately one 360° turn per inch, or twelve turns per foot. The leakdetector cable 100 therefore only requires water to be disposed along asurface by approximately one inch or more to detect the presence ofwater. The cable can be used without the helical twist, but in manyinstances would not operate as well.

The openings 112, 114 in the jacket 102 are sufficiently large to allowwater to enter and contact coverings 214, 202, respectively, whileholding the detector conductors 106, 104 in the jacket 102. Sincecoverings 214, 202 may be made from a dissimilar material from thejacket, the structure of the jacket 102 provides sufficient stability tohold the detector conductors 106, 104 in the jacket, both before andafter the leak detector cable 100 is twisted into a tight helix. Thedissimilar materials of the jacket 102 and conductive coatings 214, 202,allow easy separation, as indicated above.

For example, and not by way of limitation, the jacket 102 can be madefrom an extruded olefin based material, while the coverings 214, 202 canbe made from a highly conductive PVC plastic coating. Detectorconductors 104, 106 can be made from 24 AWG 7/32 stranded conductor to atarget diameter of 0.040 inches (nominal). The detector conductors 104,106 can be color-coded as black to distinguish the detector conductorsfrom the feedback conductors 108, 110. The feedback conductors 108, 110may comprise two 26 AWG stranded conductors that are insulated with anon-conductive PVC plastic compound to a target diameter of 0.035 inches(nominal). These feedback conductors 108, 110 can be color-coded aswhite and red to distinguish them from detector conductors 104, 106.Leak detector cable 100 is extruded in the flat layout pattern that isillustrated in FIG. 2. The diameter of the extrusion of the final jacket102 may be 0.165 inches (nominal). As mentioned above, the outer jacketmay be a polyolefin. For example, the polyolefin may be XLPE (cross-linkpolyethylene), polypropylene, low density polyethylene, medium densitypolyethylene, linear low density polyethylene, or an olefin basedderivative, such as TPE. As mentioned above, the conductors 104, 108,110, 106 are spaced evenly in a horizontal plane at the center of thejacket 102. The spacing may be approximately 0.040 inches center tocenter across the horizontal plane to provide ease in applying theinsulation displacement connector 502, illustrated in FIG. 5, which maybe an RJ-11 connector. The layout of the feedback conductors 108, 110,that have insulating coatings 206, 210 between the detector conductors104, 106, by design provides isolation between conductive coatings 202,214, especially when the leak detector cable 100 is twisted into ahelix, which, in other designs, may cause the detector conductors 104,106 to short together.

In accordance with another embodiment, the leak detector cable 100,illustrated in FIGS. 1 and 2, may use a polyolefin based conductivematerial for conductive coatings 202, 214, and a polyolefin basednon-conductive material for insulating coatings 206, 210. In accordancewith this embodiment, the jacket 102 is made from a PVC material so thatthe coatings 202, 206, 210, 214 are dissimilar to the PVC material ofjacket 102, which aids in stripping the jacket 102 from the conductors104, 106, 108, 110. In fact, a wire stripper can be used to remove thejacket 102 in both embodiments disclosed above, to expose the conductors104, 106, 108, 110, so that a connector, such as an insulationdisplacement connector 502, can be easily connected to the leak detectorcable 100. The use of PVC as jacket 102 provides a high degree of flameretardation and has very low smoke generating properties when combusted.Other materials can also be used that have disparate properties. Forexample, fluoropolymers (Teflon, PFA, Tefzel, Solef), TPE, TPR andpolyurethane. Fluoropolymers can provide maximum resistance to solvents,while the other additional plastics, in varying combinations, can beused over a wide range of temperatures, from −70° C. to 250° C.

The chart provided below indicates the pairing of possible materials ofjacket 102 with a conductive coating around the wire, as well as aninsulating cover or coating around the wire that are dissimilar and havelow affinity. Of course, mixtures of these materials can also be used.The materials can also be dry blended.

CHART 1 LEAK DETECTION CABLE MATERIALS MATRIX CONDUCTIVE/ INSULATIVECOATINGS JACKET JACKET JACKET JACKET JACKET PVC POLYOLEFIN PVDF TPE TPRPOLYOLEFIN PVC CPE TPE POLYESTER ELASTOMER FLUOROPOLYMER PVC CPE TPE TPRPOLYOLEFIN FLUOROPOLYMER POLYESTER PVDF NYLON PET POLYURETHANE ELASTOMER

Conductive coatings, such as conductive coatings 202, 214, that areextruded around the detector wires 204, 216, are extruded materialswhich contain high levels of conductive components and/or carbon black.These combinations, in varying quantities, depending upon the compoundbase, provide outstanding conductive properties. The range ofconductivity needed to provide effective volume resistivity is less than100 KOhms per foot at 20° C. The materials listed asconductive/insulative coatings in the first column can beformulated/compounded/made to have the necessary conductive properties.Hence, PVC, polyolefin and Teflon can act as either an insulativecoating or a conductive coating, as desired. The polyvinyl chloride(PVC) can be semi-rigid and flexible. Polyolefins may comprisepolyethylenes (PE), which include: low density polyethylene (LDPE),linear low density polyethylene (LLDPE), medium density polyethylene(MDPE), high density polyethylene (HDPE) and cross linked polyethylene(XLPE). Thermoplastic elastomers (TPE) may include ultra high molecularweight (UHMW) PVC based alloys. Trade names for these products includeFlexalloy and Seoprene. Polyvinylidene fluoride (PVDFP) is sold underthe tradenames Solef and Kynar. Thermoplastic rubber (TPR) is an olefinbased synthetic rubber. This material is sold under the tradenamesElexar, Telcar and Santoprene. Polyvinylidene fluoride (PVDF) is soldunder the tradenames of Solef and Kynar. Polyester and ether basedpolyurethanes are referred to as TPU. Chart 1 provides the pairing ofmaterials that are sufficiently dissimilar so as to provide a matingsystem that keeps the materials from sticking together.

Alternatively, a braided type of insulation can be used instead of solidcoating type of insulation that allows water to seep through thebraiding. The braided insulation that covers the detector wires havemultiple small openings that allow aqueous materials to penetrate thebraided cover and contact the detector wire. Hence, braided covers donot need to be constructed from a conductive material. Again, materialsthat are dissimilar to the jacket may be used for the braided cover. Thebraid can be constructed of cotton, polyester, aromaticpolyamides/meta-aramid, copolyamide, para-amide, nylon, polyethylene,polypropylene, olefin, cellulosic fiber, art silk, synthetic fibers,silicon, fluoropolymers and others materials. Dissimilar materials mayhave a large disparity in melting temperature, which can be used as aguideline for selection of some materials.

FIG. 3 illustrates another embodiment of a leak detector cable 300. Asshown in FIG. 3, jacket 302 is disposed around feedback conductors 316,318. Feedback conductors 316, 318 are disposed between detector cables308, 310. Feedback conductor 316 comprises an insulating coating 320that covers the feedback wire 322. Similarly, feedback conductor 318comprises an insulating coating 324 that covers feedback wire 326.Detector cable 308 comprises a conductive coating 312 that covers thedetector wire 314. Detector cable 310 comprises a conductive coating 328that covers the detector wire 330. The conductive coatings 312, 328 arenon-porous and protect detector cables 308, 310 from corrosion. Detectorcable 308 is disposed in an opening 304 in the jacket 302. Opening 304provides structure to interlock the detector cable 308 to the jacket302, which is substantially less than that shown in the embodimentillustrated in FIG. 2. The jacket 302 and the conductive coating 312 canbe made of plastics that have a higher degree of affinity, so that thejacket 302 holds the detector cable 308 in the opening 304. Theadvantage of the configuration illustrated in FIG. 3 is that a greaterportion of the conductive coating 312 is exposed to the outsideenvironment for detection of aqueous fluids. Opening 306 is similar toopening 304 in that jacket 302 holds the detector cable 310 in a similarmanner, but can be used with materials with greater affinity. Theembodiment of FIG. 3 also includes jacket material 302 disposed betweenthe feedback conductors 316, 318 and between detector cable 308 andfeedback conductor 316, as well as between detector cable 310 andfeedback conductor 318. This structure allows for greater isolation ofdetector cables 308, 310.

FIG. 4 is an illustration of another embodiment of a leak detectioncable 400. As shown in FIG. 4, jacket 402 surrounds detection cable 408,feedback conductor 416, feedback conductor 418 and detection cable 412.Detection cable 408 comprises a conductive layer 412, which surrounds aconductive wire 414. Detector cable 410 has a conductive layer 432 thatsurrounds the detector wire 434. Conductive layers 412, 432 arenon-porous and protect the detector wires 414, 434 from corrosion as aresult of exposure to aqueous fluids. In addition, the conductive layersincrease the surface area of conductive material that is exposed to theenvironment as compared to a smaller wire that is not covered by theconductive coating. In addition, the conductive coatings 412, 434 can beselected from a material that has greater affinity with the jacket 402to hold the detection cables 408, 410 in the jacket 402, if greateradhesion to the jacket 402 is needed, or a material that has greaterdissimilarity with jacket 402 if less adhesion is desired. In otherwords, the layers 412, 420, 424 and 432 can all be selected, as desired,to obtain the desired adhesion to the jacket 402. Feedback conductors416, 418 are disposed between the detector cables 408, 410 in ahorizontal plane, to again provide insulation, so that the detectorcables 408, 410 do not short out when the leak detection cable 400 istwisted into a helix. Optional indentations 428, 430 reduce the amountof material in the jacket 402 and provide some stability for the jacket402 when placed in the field. The optional indentations also provide anorientation for tooling and for proper stripping of the jacket 402. Inthat regard, only one indentation may be required in the jacket 402.Jacket 402 extends more than half way around the surface of thedetection cables 408, 410 to provide structural stability to lock thedetector cables 408, 410 into the jacket 402. In the embodimentdisclosed in FIG. 4, a large surface area is provided for exposure toaqueous fluids to ensure detection of these fluids.

FIG. 5 is an isometric view of a leak detection cable 500 that isconnected to an insulation displacement connector 502. The insulationdisplacement connector 502 may be an RJ-11 type connector, in which thefour flat wire configuration 504 is placed in the connector 502. Whenthe connector 502 is locked on the four flat wire configuration 504, theconnector displaces the insulation on the wires and connects theconnector 502 to the wires in an easy and simple manner.

FIG. 6 is a cutaway side view of an extrusion molding device 600. Asshown in FIG. 6, the extrusion molding device 600 comprises a die 602and a tip 604. The die 602 has an opening 606 from which the heatedpolymer is extruded as a jacket around the four flat wire array 608. Thepolymer is inserted in the die 602 at the opening 610. The polymer isheated beyond its melting point and forced at high pressure into thecavities 612, 614, 616 around the outside of the tip 604. The size andshape of the cavities is dependent upon the particular polymer that isused for the jacket. As disclosed above, olefins or PVC materials, aswell as other materials, may be used as the polymer that comprises theouter jacket. The die 602 and tip 604 are made to withstand the hightemperatures and pressures that are necessary for the extrusion process.The extrusion molding device 600 provides the ability to make acontinuous leak detection cable. Continuous lengths of as long as tensof thousands of feet can be made by the extrusion molding device 600.Not only does the ability to continuously extrude a leak detection cablein high volumes reduce the cost of the final product, the continuousextrusion design also allows for changes to be easily made in the typeof plastic compounds that are used in the final design. The continuousextrusion process allows designers to incorporate various materials intothe product based upon the environment in which the product will beused. For example, leak detection cables for detecting aqueous fluidsmay also require chemical resistance, oil or hydrocarbon resistance,acid resistance, sunlight or UV resistance, varying temperature rangesand weather resistance. The materials selected for the jacket and forthe conductive coatings can be selected based upon the environment ofthese uses. In other words, different plastic compounds can be simplyinserted in the opening for the jacket polymer 610 to change the jacketmaterial during the extrusion process.

The extrusion molding device 600 uses a round conventional methodologyfor the extrusion process, which is common in wire and cable extrusionprocesses. In addition, profile extrusion methodology is also used,which is more commonly used in the profile industry for making productssuch as weather stripping, picture frames, molding, door seals, windowseals, etc. Hence, the extrusion molding device 600 incorporates twodifferent design technologies, i.e., round conventional extrusionmethodology and profile methodology.

In addition, the continuous extrusion process is also utilized to makethe wires that are used in the four flat wire array 608. Theseextrusions are done prior to the final assembly of the product in theextrusion molding device 600. As set forth above, the tip 604 guides andaccommodates the four flat wire array 608 to be strategically located inthe positions that result in the profiles illustrated in FIGS. 2, 3 and4, and as disclosed more fully below. The manner in which the tip anddie operate together results in the cross-sectional shapes illustratedin FIGS. 2, 3 and 4, so that a desirable surface area of the conductivemembers is exposed to the environment and the detector wires areinsulated from each other, as well as from the non-conductivecomponents.

Close-up portion 700 of FIG. 6 is illustrated in FIG. 7. As shown inFIG. 7, a portion of the tip is illustrated in an enlarged, close-upview, showing the four flat wire array 608. Each of the wires has eithera conductive coating or a non-conductive coating already applied in thestandard manner in which insulation is applied to wires. The four flatwire array 608 is fed through the opening in the tip, as shown in FIG.7. Spacers 702, 704, 706 separate the wires so that the center to centerspacing substantially matches the spacing required for an insulationdisplacement connector, such as an RJ-11 connector. As shown in FIG. 6,the four flat wire array 608 is then fed through the die opening 606,where the polymer is extruded around the four flat wire array 608. Thespacers 702, 704 and 706 carefully hold the four flat wire array 608 sothat the four flat wire array 608 is strategically placed with respectto the die opening 606, illustrated in FIG. 8.

FIG. 8 is a close-up view of the end of the die 602. As shown in FIG. 8,the die 602 has a die opening 606, which matches the cross-sectionalshape of the leak detection cable. Optional indentations (not shown) mayalso be included in die 602. The polymer is extruded through the dieopening 606 around the four flat wire array that is centered in ahorizontal plane across the middle of the die opening 606. The indentedportion shown in the die opening 606 corresponds to the openings thatare adjacent to the detector wires, as illustrated in FIG. 2. The dieopening 606 can be formed by electrical discharge machining. The preciseshape provides for the final shape of the extruded jacket. The twodetector wires located on the outside of the four flat wire array 608rub against the tabs 802, 804 of the die 602 during the extrusionprocess. Spacers 702, 706 (FIG. 7) hold the detector wires to producethe proper spatial orientation of the detector wires and tabs 802, 804.Since the detector wires on the outside of the four flat wire array 608rub against the tabs 802, 804, the plastic of the jacket is preventedfrom coating the lateral outside surfaces of the detector wires. Tabs802, 804 disallow the flow of the plastic of the jacket over theconductive members in those areas so that a desired portion of theconductive surface areas are exposed, while still providing a sufficientamount of structure to hold the detector wires in the jacket. Uponexiting the die 602, the assembled leak detection cable is cooled infree air and a water bath. The die 602 provides the final shape of thejacket prior to being twisted into a helix. The tip 604 (FIG. 6), asexplained above, must be carefully mated to be compatible with the dieto provide precise center to center spacing and to maintain each of theconductors in their prescribed locations. In addition, the die must bedesigned to have die angles and dimensions that can be modified to allowthe use of plastics with different viscosities and flow rates to beshaped during the extrusion process. The extrusion process also allowsfor color coating of all components, which eliminates confusion in thefield.

FIG. 9 discloses another embodiment of a leak detection cable 900. Asdisclosed in FIG. 9, the leak detection cable comprises a jacket 902that has openings 904, 906, in which detector cables 908, 910 aredisposed, respectively. In addition, the leak detection cable 900includes feedback conductors 924, 926. Detector cables 908, 910 includedetector wires 912, 914 that are surrounded by a protective, conductivepolymer layer 916, 918, respectively. In addition, detector cables 908,910 may include optional non-conductive, liquid pervious layers 920,922. Either one, both or neither of the detector cables 908, 910 mayinclude the optional non-conductive, liquid pervious layer. The purposeof the option, non-conductive, liquid pervious layer is to provide anon-conductive layer that assists in preventing false detection of leaksresulting from non-liquid contaminants and residues that would otherwiseprovide a conductive path between conductive polymer layer 916 andconductive polymer layer 918. The optional non-conductive, liquidpervious layers 920, 922 may comprise woven or braided polymer strandsthat have spaces allowing aqueous solutions to penetrate and contact theconductive polymer layers 916, 918. The strands are non-hydroscopicstrands so that the strands do not absorb water and dry easily. Thestrands may be made from a material that has affinity to the material ofthe jacket 902. The combination of materials listed above can be usedfor this purpose. In this fashion, the optional non-conductive, liquidpervious layers 920, 922 insulate the conductive layers 916, 918 fromcontact from non-liquid conductive materials, including contaminants andresidues.

Alternatively, the optional, non-conductive, liquid pervious layers 920,922, that are illustrated in FIG. 9, may comprise a continuous, porous,non-conductive polymer that surrounds and isolates the conductivepolymer layers 916, 918 and conductively isolates the conductive polymerlayers 916, 918 from non-liquid materials, including contaminants andresidues. The continuous, porous polymer coating may be obtained fromNorthwire, Inc., Osceola, Wis., and Putnam Plastics, Dayville, Conn. Thecontinuous, porous polymer covering includes numerous pores that allowthe passage of aqueous fluids to the conductive polymer layers 916, 918.The pores in the continuous, porous polymer covering are substantiallysmaller than the spaces between the braided fibers. The continuous,porous, non-conductive polymer covering is non-hydroscopic, so that thedetector cables 908, 910 are easily dried out.

FIG. 9 also includes feedback conductors 924, 926. Feedback conductors924, 926 include feedback wires 928, 930, as well as an optionalinsulating coating 932, 934, respectively. If the optional insulatingcoating 932, 934 is employed, the feedback conductors 924, 926 can beplaced closely to each other, as well as closely to the openings 904,906, as disclosed in FIG. 3. Alternatively, feedback wires 928, 930 canbe embedded in the jacket 902 and thereby insulated from the sensorcables. Further, if the optional insulated coatings 932, 934 are notused, and if the optional, non-conductive, liquid pervious layers 920,922 are used on both detector cables 908, 910, which provides aconductive insulation, the feedback wires 928, 930 can be disposedadjacent to the openings 904, 906.

Hence, the embodiments disclosed herein provide a leak detection cablein which the outer jacket can be easily removed to expose a four flatwire configuration that has the proper spacing to connect to a standardfour flat wire insulation displacement connector. The detector cablesare covered with a conductive coating, which increases the conductivesurface area of each conductor by approximately 40%. The extrudedconductive coating therefore provides a greater surface area fordetection of aqueous fluids. In that regard, the greater surface areaallows for a larger cross-section of the conductive plastic material tobe entrapped and locked in the extruded jacket, to provide aninterlocking construction that allows the conductive extrusion of thedetector cables to remain solidly within the jacket, even though thejacket is twisted in a tight helix. Further, the conductive coatingprotects the metallic copper conductive wires of the detector cablesfrom oxidation by shielding the conductive copper wires from air andmoisture. The dissimilar materials used for the jacket, as compared tothe coatings on the detector and feedback wires, allow the jacket to beeasily stripped away from the wires without disturbing the integrity ofthe coatings of the wires. The plastic materials described provideresistance to a variety of chemicals, petroleum products, oils, acidsand other corrosive fluids. In this manner, an inexpensive and easilyconstructed leak detection cable can be provided that is easily adaptedfor quick installation in the field. Also, a cross-linked polymer isused for the jacket so that the jacket can be heated and twisted, andremains in a helix after the jacket has cooled.

The foregoing description of the invention has been presented forpurposes of illustration and description. It is not intended to beexhaustive or to limit the invention to the precise form disclosed, andother modifications and variations may be possible in light of the aboveteachings. The embodiment was chosen and described in order to bestexplain the principles of the invention and its practical application tothereby enable others skilled in the art to best utilize the inventionin various embodiments and various modifications as are suited to theparticular use contemplated. It is intended that the appended claims beconstrued to include other alternative embodiments of the inventionexcept insofar as limited by the prior art.

1. A leak detection cable comprising: a first detector conductorcomprising: a first detector wire; a first conductive coveringsurrounding said first detector wire that comprises a preselectedconductive plastic; a first feedback conductor disposed adjacent to saidfirst detector wire that defines a plane with said first detectorconductor comprising: a first feedback wire; a first insulating coveringsurrounding said first feedback wire that comprises a preselectednon-conductive plastic; a second feedback conductor disposed in saidplane adjacent to said first feedback conductor comprising: a secondfeedback wire; a second insulating covering surrounding said secondfeedback wire that comprises said preselected non-conductive plastic; asecond detector conductor disposed in said plane adjacent to said secondfeedback conductor comprising: a second detector wire; a secondconductive covering surrounding said second detector wire that comprisessaid preselected conductive plastic; a jacket that surrounds said firstfeedback conductor and said second feedback conductor and partiallysurrounds said first detector conductor and said second detectorconductor by an amount that is sufficient to hold said first detectorconductor and said second detector conductor and provides openingsadjacent to said first conductive covering and said second conductivecovering to allow exposure to aqueous fluids, said jacket made from aplastic jacket material that is dissimilar to, and has low adhesionwith, said preselected conductive plastic and said preselectednon-conductive plastic so that said jacket can be easily removed fromsaid first detector conductor, said second detector conductor, saidfirst feedback conductor and said second feedback conductor.
 2. The leakdetector cable of claim 1 wherein said jacket is twisted in a helicalconfiguration so as to sequentially expose said first detector conductorand said second detector conductor.
 3. The leak detection cable of claim1 wherein: said preselected conductive plastic and said preselectednon-conductive plastic comprise polyvinyl chloride; and, said plasticjacket material is selected from the group comprising: polyolefin, PVDF,TPE and TPR.
 4. The leak detection cable of claim 1 wherein: saidpreselected conductive plastic and said preselected non-conductiveplastic comprise polyolefin; and, said plastic jacket material isselected from the group comprising: PVC, CPE and TPE.
 5. The leakdetection cable of claim 1 wherein: said preselected conductive plasticand said preselected non-conductive plastic comprise fluoropolymers;and, said plastic jacket material is selected from the group comprising:PVC, CPE, TPE, TPR and polyolefin.
 6. The leak detector cable of claim 1wherein said first detector conductor, said second detector conductor,said first feedback conductor and said second feedback detector have asubstantially equal center to center spacing that is substantially equalto a spacing required for an insulation displacement connector.
 7. Theleak detector cable of claim 1 wherein said first conductive coveringand said second conductive covering comprise conductive coatings.
 8. Theleak detector cable of claim 1 further comprising: a non-conductive,liquid pervious layer that surrounds at least one of said firstconductive covering and said second conductive covering.
 9. A leakdetection cable comprising: at least one detector conductor comprising:a detector wire; a conductive covering surrounding said detector wirethat comprises a preselected conductive plastic; at least one feedbackconductor disposed adjacent to said detector wire that defines a planewith said detector conductor comprising: a feedback wire; an insulativecovering surrounding said feedback wire that comprises a preselectednon-conductive plastic; a jacket that surrounds said at least onefeedback conductor and partially surrounds said at least one detectorconductor by an amount that is sufficient to hold said at least onedetector conductor and provides an opening adjacent to said conductivecoating to allow exposure to aqueous fluids, said jacket made from aplastic jacket material that is dissimilar to, and has low adhesionwith, said preselected conductive plastic and said preselectednon-conductive plastic so that said jacket can be easily removed fromsaid at least one detector conductor and said at least one feedbackconductor.
 10. The leak detector cable of claim 9 wherein said jackettwisted in a helical configuration so as to sequentially expose said atleast one detector conductor.
 11. The leak detection cable of claim 10wherein: said preselected conductive plastic and said preselectednon-conductive plastic comprise polyvinyl chloride; and, said plasticjacket material is selected from the group comprising: polyolefin, PVDF,TPE and TPR.
 12. The leak detection cable of claim 10 wherein: saidpreselected conductive plastic and said preselected non-conductiveplastic comprise polyolefin; and, said plastic jacket material isselected from the group comprising: polyvinylchloride, CPE and TPE. 13.The leak detection cable of claim 10 wherein: said preselectedconductive plastic and said preselected non-conductive plastic comprisefluoropolymers; said plastic jacket material is selected from the groupcomprising: PVC, CPE, TPE, TPR and polyolefin.
 14. The leak detectioncable of claim 10 further comprising: a non-conductive, liquid perviouslayer that surrounds said conductive covering.
 15. A leak detectioncable comprising: a first detector conductor comprising: a firstdetector wire; a first conductive covering surrounding said firstdetector wire; a second detector conductor comprising: a second detectorwire; a second conductive covering surrounding said second detectorwire; a jacket that partially surrounds said first detector conductorand said second detector conductor by an amount that is sufficient tohold said first detector conductor and said second detector conductorand provides openings adjacent to said first conductive covering andsaid second conductive covering to allow exposure to aqueous fluids,said jacket made from a plastic jacket material that is dissimilar to,and has low adhesion with, said first conductive covering and saidsecond conductive covering so that said jacket can be easily removedfrom said one first detector conductor and said second detectorconductor.
 16. The leak detection cable of claim 15 wherein: said jacketis twisted in a helical configuration so as to sequentially expose saidfirst detector conductor and said second detector conductor.
 17. A leakdetection cable comprising: a first detector conductor comprising: afirst detector wire; a first detector covering surrounding said firstdetector wire; a first feedback conductor disposed adjacent to saidfirst detector wire that defines a plane with said first detectorconductor comprising: a first feedback wire; a first insulating coveringsurrounding said first feedback wire that comprises a preselectednon-conductive plastic; a second feedback conductor disposed in saidplane adjacent to said first feedback connector comprising: a secondfeedback wire; a second insulating covering surrounding said secondfeedback wire that comprises said preselected non-conductive plastic; asecond detector conductor disposed in said plane adjacent to said secondfeedback connector comprising: a second detector wire; a second detectorcovering surrounding said second detector wire; a jacket that surroundssaid first feedback conductor and said second feedback conductor andpartially surrounds said first detector conductor and said seconddetector conductor by an amount that is sufficient to hold said firstdetector conductor and said second detector conductor and providesopening adjacent to said first detector covering and said seconddetector covering to allow exposure to aqueous fluids, said jacket madefrom a plastic jacket material that is dissimilar to, and has lowadhesion with, said detector covering and said preselectednon-conductive plastic so that said jacket can be easily removed fromsaid first detector conductor, said second detector conductor, saidfirst feedback conductor and said second feedback conductor, said jackettwisted in a helical configuration so as to sequentially expose saidfirst detector conductor and said second detector conductor.
 18. Theleak detector cable of claim 17 wherein said first detector covering andsaid second detector covering comprise conductive coatings made from apreselected conductive plastic.
 19. The leak detector cable of claim 17wherein said first detector covering and said second detector coveringcomprise a braided covering.